It is well-known that birds tend to perch on any supporting surface they find on buildings, even the narrowest ones, and it is known how much trouble this causes.
One of the most efficient ways to prevent such nuisances consists in providing for, on the surface whereon bird perching is unwanted, a device on which some regions have a certain electric potential. Since the birds cannot, at the risk of having unpleasant or even harmful sensation, stay in contact with such charged regions, the repelling action is thus performed.
Such a device can be found, for example, in the TAPO-ES.RTM. commercial product, comprising a base made of an insulating material, and two rails made of an electrically conductive material, whereon a potential difference is applied, said rails, interdependent with the base, stretching in the plane of the latter. The two rails are close enough so that a bird perching on the device receives a dissuasive electric discharge. However, such a device has the following drawbacks: First, birds sometimes pile debris like twigs or other plant matter on the charged rails, for example to make a nest, that forms an insulating layer that reduces the efficiency of the device. Second, insofar as birds must touch both charged rails to get a repelling effect, the device must cover the whole surface on which perching is unwanted, leaving no uncovered surface, and thus leading to a costly installation. It is therefore an object of the invention to provide a device free of these drawbacks.